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Title:: Geochemical Characteristics and Petrogenesis of Carboniferous Volcanic Rocks from Beizhan Iron Deposit of West Tianshan

Author(s):: ZHANG Bo; JING De-long; WANG Bang-yao; JIANG Chang-yi; ZHAO Zhen-gang; 1. School of Earth Science and Resources, Chang’an University, Xi’an 710054, Shaanxi, China; 2. Key Laboratory of Western Mineral Resources and Geological Engineering of Ministry of Education, Chang’an University, Xi’an 710054, Shaanxi, China; 3. No.11 Geological Party, Xinjiang Bureau of Geology and Mineral Resources, Changji 831100, Xinjiang, China

Keywords:: geochemistry; petrogenesis; Carboniferous; volcanic rock; continental arc; West Tianshan; Xinjiang

Abstract:: Carboniferous volcanic rocks are exposed in Beizhan iron deposit of the eastern Awulale, West Tianshan. The petrology and geochemistry characteristics of major and trace elements of Carboniferous volcanic rocks were studied to discuss the tectonic settings and petrogenesis of magmatic source. The results show that most of volcanic rocks belong to middle high-K calc-alkaline and shoshonite series; the characteristics include rich in LREE and LILE (Rb, Th and K, etc.), and depleted in HFSE (Nb, Ta and Ti, etc.). Rock association and geochemistry show that volcanic rocks form in active continental arc settings, which have a close correlation with the B-type subduction of North Tianshan oceanic basin towards the south beneath Yili plate during the Late Early Carboniferous. ε_Nd(t) of volcanic rock is 0.73-4.33, suggesting that the origin magma comes from the depleted mantle. The parent magma has also experienced fractional crystallization and crustal contamination in the process of evolution.